#include <bits/stdc++.h>

using namespace std;

const int N = 5010;
int n ,m;
int a[N][N];
int f[N][N];

int main ()
{
	cin  >> n >> m;
	int k = n;
	while(k--)
	{
		int x, y ,v;
		cin >> x >> y >> v;
		x++,y++;
		a[x][y] += v;
	}
	
	for(int i = 1 i <= n; i++)
	{
		for(int j = 1; j <= n;j++)
		{
			f[i][j] = f[i-1][j] + f[i][j-1] - f[i-1][j-1] + a[i][j];
		}
	}
	int ret = 0;
	m = min(m,n);
	for(int x2 = m; x2 <= n; x2++)
	{
		for(int y2 = m; y2 <= n;y2++)
		{
			int x1 = x2-m+1,y1 = y2-m+1;
			ret = max(ret,f[x2][y2] - f[x1-1][y2] - f[x2][y1-1] + f[x1-1][y1-1]);
		}
		
	}
	
	cout  << ret <<endl;
	
	return 0;	
} 
